458 GERMINATION OF A SEED. 



existence and nature of a special principle of organization. The conclu- 

 sions at which we shall arrive, though apparently very different from 

 what we might have expected, are the necessary consequences of the 

 physical doctrine. 



It may, perhaps, aid the reader if I give, at the outset, a synopsis of 

 Outline of the ^ e argument. Selecting as a general illustration the famil- 

 argument. ia r case O f the germination of a seed and the growth of a 

 plant, we shall investigate the results of growth, in light and darkness, 

 with their attendant phenomena. From this we shall draw apparent ev- 

 idence of the existence of a special principle of organization, or plastic 

 power, and ascertain, in a general way, its functions ; but, from an ex- 

 amination of the attitude in which the resulting organism stands, as re- 

 spects its individuality, we shall learn to correct that view, and reach the 

 final conclusion that that plastic power is not an agent, but a condition 

 of things, the result or the manifestation of antecedent physical influ- 

 ences. 



Every living being springs from a germ. The animal and vegetable 

 Primordial kingdoms present us with numberless forms, differing from one 

 cel1 - another in aspect, in construction, and in function ; but the or- 



igin of all is the same a cell or vesicle, which, under the influence of 

 external circumstances, develops into a determinate shape. 



A seed may be kept in a dry place for many years without undergo- 

 ing any visible change, or losing its power of germination. It may be 

 exposed to all the annual variations of temperature occurring in the dif- 

 ferent seasons ; it may have the free access of atmospheric air. Its vi- 

 tality is dormant ; there is no attempt at evolving its parts. 



But if some water be supplied, and a certain degree of dampness be 

 Germination thereby communicated, the seed does not fail, as soon as the 

 of a seed. temperature reaches that of a summer's day, to germinate. 

 Under the influence of air, heat, and moisture, the embryo consumes the 

 nourishment stored up for it in the seed, a gradual unfolding of its parts 

 ensues, a root is put forth, a stem rises from the ground, and leaves 

 make their appearance : so heat, air, and water have enabled the seed to 

 become a plant. 



These physical agents are not, however, sufficient to carry the growth 

 Effects of sun- forward to its full extent. Another is essential : it is light ; 

 light. f or if g row th be conducted in darkness, heat, air, and water 



can not cause the young plant to add any thing to its substance. It is 

 feeding on the seed. Indeed, when the experiment is carefully made, it 

 is found that there is an actual loss of substance, the resulting plant, if 

 dried, weighing less then than the dry seed from which it came. 



